Expansion of Working Memory Capacity Supports Early Skill Learning

Real-world motor skills depend on the precise spatiotemporal coordination of action sequences refined through practice. Working memory, which transiently maintains and manipulates task-relevant information, supports skill acquisition expanding with extensive training, as shown in expert domains such as in master chess players. Yet, the temporal dynamics of working memory emergence and expansion during the rapid performance gains that define early skill learning remain unclear.

We addressed this question across three experiments in which participants learned various naturalistic sequential keypress skills. Within each practice trial, we observed segments of high-initial-skill (HIS)—transient periods of elevated performance followed by skill drops—that persisted throughout training. The keypress content of HIS segments scaled with execution speed and systematically increased with practice, reflecting an expansion of keypress chunk content consistent with the progressive enlargement of working memory capacity. Importantly, HIS segment keypress content continued to rise even after overall performance plateaued. Theta–gamma phase–amplitude coupling (θ/γ PAC) and beta (β)-band bursts, mechanisms implicated in maintaining and binding individual actions into sequences in working memory, were elevated during HIS segments with hippocampal θ/γ PAC predicting HIS segment content.

Our results suggest that working memory capacity expands during early learning of a naturalistic skill and continues strengthening with practice after skill plateau is reached, possibly supported by hippocampal theta/gamma phase-amplitude coupling.